As the mourning period to commemorate the 1994 death of Kim Il Sung was approaching, citizens who were visiting Pyongyang were ordered to leave. Only Pyongyang residents were allowed to remain in the capital city during this time of mourning. The period lasts from July 6th through July 13th.
The North Korean government normally restricts domestic travel for one or two weeks during all periods of "special vigilance", which include special dates pertaining to Kim Il Sung and Kim Jong Il, as well as when foreign heads of state visit the country.
Source: Daily NK